A crow’s nest is a structure in the upper part of the ship, especially old-fashioned ones. It is used as a lookout point and positioned high above to increase visibility over the curvature of the Earth.
On the deck of a ship 4 m (13 ft) above the surface of the ocean, an observer can spot a 20 m (66 ft) high ship from at most ±25 km (16 mi). On the other hand, from a 35 m (115 ft) high crow’s nest, an observer will be able to spot the same ship from ±40 km (25 mi) away.
On modern ships, the role of a lookout is replaced by radars. And for the same reason, a radar is positioned in the upper part of a ship.
Continue reading “Crow’s Nest on Ships”
Before sunrise or after sunset, the Sun is below the horizon and not directly visible. But the sky and clouds above are illuminated because they are high above, and sunlight can reach them.
If there’s a mountain between the Sun and the clouds, it can cast a shadow on the clouds. The flat-Earth model assumes the Sun is always high above, and thus, this phenomenon cannot possibly occur in a flat-Earth.
The fact that a mountain can cast its shadow on clouds far above it is evidence that the Earth is spherical.
Continue reading “Shadow on Clouds”
The surface of the water in a glass of water is practically flat. Some flat-Earthers claim this is ‘evidence’ that the surface of the water is flat, and it will always be flat no matter how wide the container. They are wrong.
If the Earth is a sphere with the radius of 6371 km (3960 miles), then the surface of the water in a 10 cm (4 in) wide glass will have a bulge of 0.00000002 cm as the result of gravity, excluding other effects like the surface tension.
Continue reading “A Glass of Water”
Turning Torso is a 190 m (623 ft) high building in Malmö, Sweden. It is situated near the strait of Øresund. At the other side of the channel lies the city of Copenhagen, Denmark, only 15 km (9 miles) away from Malmö. Turning Torso has a distinctive segmented shape that is easy to recognize from far. And more importantly for our purposes, the segmented form is making it easy to judge its height from far.
Continue reading “Evidence of Curvature: Turning Torso Building, Malmö, Sweden”
We can’t directly observe and subjectively perceive the curvature of the Earth from a position close to the surface. And this matches the expectations in the spherical Earth model.
Flat-Earthers often take the fact we can see the curvature by standing on a beach as ‘evidence’ the curve doesn’t exist. They are, once again, wrong.
Continue reading “The Reason We Cannot See Earth’s Curvature When Standing on a Beach”
A fisheye lens distorts images. It results in images having barrel distortions. In a fisheye lens, a straight line can appear curved. But some flat-Earthers don’t realize that the opposite is also true, a fisheye lens can easily make a curved line look straight.
Continue reading “Fisheye Lenses Can Make Curved Lines Appear Flat”
Atmospheric refraction causes a distant object to appear higher than its actual position. As a result, the object can be physically behind Earth’s curvature but is still visible because the light coming from it is refracted by the atmosphere.
There are many curvature calculators and simulation tools that don’t account for refraction. They would give us the correct results indicating the object’s physical positions but fail to show us the correct apparent position of the object when visually observed.
Flat-Earthers are often too happy with the calculator showing them the results they want to see and fail to see the reason for the discrepancy.
Continue reading “Curvature Calculators and Atmospheric Refraction”
The Mississippi River never flows uphill, or in other words, ascend to a location farther from sea level anywhere in the Mississippi River basin.
Flat-Earthers often claim that if the Earth is spherical, then the Mississippi River will have to flow uphill to overcome the curvature of the Earth. They are wrong.
Continue reading “The Earth is Spherical and The Mississippi River Never Flows Uphill Anywhere”
If the Earth is flat, then the Sun would have been visible from the entire Earth, but that’s not the reality. So, to rescue the concept of the flat-Earth from being falsified, they invented an ad-hoc hypothesis that the Sun appears to set because of perspective and refraction.
Continue reading “Atmospheric Refraction and the Position of the Sun in the Flat-Earth Model”
As the Earth is spherical, the horizon is below the eye-level (or the astronomical horizon). The angle between the eye-level and the horizon is the dip of the horizon. The angle becomes larger as we go higher.
Flat-Earthers often claim that “the horizon always rises to eye-level”, and thus ‘proving’ the flat Earth claim. Despite their insistence to use a water level to ‘prove’ water is flat, the same device can be used to demonstrate the dip of the horizon, proving the water surface has curvature, and consistent with the spherical Earth model.
Continue reading “Water Level Demonstrates The Dip of the Horizon and Proves Earth’s Curvature”
Soundly’s pictures and videos of Lake Pontchartrain power lines and causeway stirred up the flat-Earthers’ nests. They clearly show the curvature of the Earth, where it is usually hard to discern. For the rest of us, those pictures are just the consequence of the fact that the Earth is a globe.
Flat-Earthers can’t take this, and they invented various excuses to attack the credibility of these pictures and videos. Some of them look for specific vantage point where it is impossible or very hard to discern the curvature. They would conclude if the curve is not seen from these vantage points, then it should not be visible from Soundly’s viewpoints.
Continue reading “Perspective Compression: Determining If a Curvature Exists”
High-altitude balloon footage is often abused by flat-Earthers to show us that the Earth is flat when seen from a high altitude.
We analyzed more than two dozens of footage taken from high-altitude balloons on YouTube, and we can easily conclude the curvature is there and usually easy to spot, including in the cases where flat-Earthers use the video as ‘proof’ of a flat Earth.
Continue reading “Curvature of the Horizon in High-Altitude Balloon Footage”
In 205 BC, Eratosthenes successfully determined the circumference of the Earth by measuring the length of the shadow cast by a rod. He did the measurement in Alexandria and timed it to coincidence when the Sun is directly overhead Syene.
2222 years after that, some flat-Earthers tried to refute the Eratosthenes experiment. They say the experiment can be applied to the flat-Earth model.
Continue reading “The Eratosthenes Experiment: Proving the Earth is Spherical”
Flat-Earthers mention the curvature of water a lot. According to them, the curve of the water can never be observed, and thus, the Earth is flat.
The problem with such an argument is that they usually conclude that from a very small amount of water. Water in a glass or a bucket will practically look flat. Not because there is no curvature due to Earth’s gravity, but because the water is in such small amount so that the curvature is minuscule and impossible to observe, let alone with the naked eye.
Continue reading “The Curvature of the Water Surface”
The Amazon never flows uphill, or in other words, ascend to a location farther from sea level anywhere in the Amazon basin.
Flat-Earthers often claim that if the Earth is spherical, then the Amazon will have to flow uphill to overcome the curvature of the Earth. They are wrong.
Continue reading “The Earth is Spherical and The Amazon Never Flows Uphill Anywhere”
Gravity causes water to seek the lowest potential, which can be simplified as the position as close as possible to the Earth’s center of gravity. As a result, the surface of the water will have equipotential surface and form an approximately spherical surface which has the same center as the Earth. Every location along the surface has the same potential.
Continue reading “Equipotential: a Property of the Surface of Water”
Light waves are not always moving in a straight line. When it passes through a medium of a different refractive index, the waves will deviate. The phenomenon is called refraction and described according to Snell’s Law.
Earth’s atmosphere has variation in air density that depends on the altitude. As the refractive index changes with the density of the medium, light waves passing through Earth’s atmosphere also experience refraction.
Continue reading “Atmospheric Refraction”
If we can’t see a distant ship, then it is because of one of these reasons:
- Our eyes have limited angular resolution and are unable to resolve the ship at that distance.
- The atmospheric condition is limiting our visibility.
- The curvature of the Earth obscures the ship.
Flat-Earthers are keen to demonstrate that a previously invisible ship at a distance can be made visible by zooming in. They take this fact as ‘proof’ that the curvature of the Earth doesn’t exist. They are wrong. The curvature of the Earth is not the only reason a distant object is not visible.
Continue reading “Zooming In On Distant Ships Does Not Disprove Earth’s Curvature”
In 1870, Alfred Russell Wallace successfully demonstrated the curvature of the Earth to answer the challenge put forward by a flat-Earther, John Hampden.
Continue reading “Bedford Level Experiment Confirmed the Curvature of the Earth”
Wi-Fi is one of the most common ways of getting connected to the Internet. Practically all short-range wireless network use WiFi. Using specialized equipment, Wi-Fi is usable over a very long distance, even over hundreds of miles.
When designing a long-range Wi-Fi link, we must account for the curvature of the Earth.
Continue reading “Long-Range Wi-Fi and the Curvature of the Earth”